The present disclosure relates to a stereoscopic image capturing apparatus which captures stereoscopic images, and more particularly to a focus adjustment technique when stereoscopic images are captured.
In recent years, there has been increasing demand for cameras (stereoscopic image capturing apparatuses) capable of capturing 3D (stereoscopic) images. As methods of capturing stereoscopic images, there have been used a beam splitter type (half mirror type) of capturing images using a half mirror, a side-by-side type (parallel two-lens type) of capturing images using two imaging apparatuses which are physically arranged and installed, and the like. In these types, the imaging apparatuses are mounted on a cradle called a rig and photographing is performed, and thus the degree of freedom of installation of the imaging apparatuses is increased. For example, a distance between two lenses (hereinafter, referred to as an IAD (Inter Axial Distance)) capturing stereoscopic images, convergence, or an angle view can be selected with a high degree of freedom.
However, there is a problem in that whereas the degree of freedom is high, great effort and time are necessary for settings and adjustments for each photographing in order to mount the stereoscopic image capturing apparatuses on the rig. In addition, there is also a problem in that particularly the beam splitter type rig is a large-scale device, and is not suitable for photographing or coverage in the field.
In order to solve the problems, there are cases where a so-called integrated two-lens 3D camera is manufactured in which two 2D image capturing cameras which perform photographing in the side-by-side type are assembled into one casing. In the integrated two-lens 3D camera manufactured in this way, assembly is not necessary, and alignment adjustment (optical axis adjustment of the left and right cameras) is not also necessary. Further, since the integrated two-lens 3D camera is compact, it is advantageous in that it is easy to carry in the field when photographing or coverage is performed, and photographing can be performed with a short setup time.
However, the integrated two-lens 3D camera basically employs the side-by-side type, and thus there is a limitation on adjustment of an IAD. In other words, since the respective optical systems or imagers of the two lenses physically interfere with each other, the IAD may not be shorter than a specific distance defined by arrangement positions of the optical systems or imagers. For this reason, for example, in a case of very near photographing of a subject, since a parallax amount of a background image located on the rear side of the subject is excessive even if a parallax amount is adjusted to zero by matching convergence to the subject, the parallax amount exceeds a parallax range where people view 3D images with comfort.
As the case where a distance between the subject and the stereoscopic image capturing apparatus is very short, for example, there may be a case of interview photographing of a figure, a case of photographing in the background in the sports relay, or the like. In this case, a distance between the subject and the imaging apparatus is about 1 to 2 m, and a convergence point is also adjusted to a distance of about 1 to 2 m. In this case, it is said that the most useful IAD for putting parallax in a range where people can view 3D image with comfort is 10 mm to 40 mm. However, in the integrated two-lens 3D camera at present, it is difficult to realize such a short IAD while maintaining image quality or functions, that is, without reducing a lens diameter or an imager size.
In a case of performing photographing using the beam splitter type, two imaging apparatuses do not physically interfere with each other, and thereby it is possible to much shorten an IAD. As described above, however, there is the problem in that great efforts and time are necessary for settings and adjustments for each photographing, and thus there remains the problem in terms of not being suitable for interview photographing of a figure, or photographing in the backyard in the sports relay.
For'example, Japanese Unexamined Patent Application Publication No. 2003-5313 discloses a stereoscopic image capturing apparatus where a convergence point can be adjusted to any position in a state where a focal point of a camera is matched with the convergence point of two lenses. If this apparatus is used, photographing can be performed with an IAD equal to the pupil distance of a person, and thus it is possible to capture images where a natural stereoscopic effect can be obtained even in a case of near photographing.